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authorRich Felker <dalias@aerifal.cx>2011-04-04 16:24:49 -0400
committerRich Felker <dalias@aerifal.cx>2011-04-04 16:24:49 -0400
commitbd57e2b43a5b56c00a82adbde0e33e5820c81164 (patch)
tree38cbea7e455183a890bc2293ca1f959816158fa2
parent5600088d387491bd0af1879aa64e5d388805d8ec (diff)
downloadmusl-bd57e2b43a5b56c00a82adbde0e33e5820c81164.tar.gz
use a local temp buffer for unbuffered streams in vfprintf
this change makes it so most calls to fprintf(stderr, ...) will result in a single writev syscall, as opposed to roughly 2*N syscalls (and possibly more) where N is the number of format specifiers. in principle we could use a much larger buffer, but it's best not to increase the stack requirements too much. most messages are under 80 chars.
-rw-r--r--src/stdio/stderr.c1
-rw-r--r--src/stdio/vfprintf.c13
2 files changed, 14 insertions, 0 deletions
diff --git a/src/stdio/stderr.c b/src/stdio/stderr.c
index 3bdaffbc..9a70700c 100644
--- a/src/stdio/stderr.c
+++ b/src/stdio/stderr.c
@@ -6,6 +6,7 @@ static FILE f = {
.buf_size = 0,
.fd = 2,
.flags = F_PERM | F_NORD,
+ .lbf = -1,
.write = __stdio_write,
.seek = __stdio_seek,
.close = __stdio_close,
diff --git a/src/stdio/vfprintf.c b/src/stdio/vfprintf.c
index 57878c03..8cbfd96e 100644
--- a/src/stdio/vfprintf.c
+++ b/src/stdio/vfprintf.c
@@ -627,13 +627,26 @@ int vfprintf(FILE *f, const char *fmt, va_list ap)
va_list ap2;
int nl_type[NL_ARGMAX] = {0};
union arg nl_arg[NL_ARGMAX];
+ unsigned char internal_buf[80], *saved_buf = 0;
int ret;
va_copy(ap2, ap);
if (printf_core(0, fmt, &ap2, nl_arg, nl_type) < 0) return -1;
FLOCK(f);
+ if (!f->buf_size) {
+ saved_buf = f->buf;
+ f->buf = internal_buf;
+ f->buf_size = sizeof internal_buf;
+ }
ret = printf_core(f, fmt, &ap2, nl_arg, nl_type);
+ if (saved_buf) {
+ f->write(f, 0, 0);
+ if (!f->wpos) ret = -1;
+ f->buf = saved_buf;
+ f->buf_size = 0;
+ f->wpos = f->wbase = f->wend = 0;
+ }
FUNLOCK(f);
va_end(ap2);
return ret;